ARM: dts: msm: Add ADC support for SDX hedgehog

Clients of VADC_HC include reading voltage phone
power, system thermistors for thermal mitigation such as
pa_therm, case_therm, XO therm, vph_pwr. Add the supported
VADC channels for the sdxhedgehog platform.

Change-Id: Ia4e3ff14e9149250038301fafd467d4913aaf221
Signed-off-by: Sriharsha Allenki <sallenki@codeaurora.org>